FYI, the more common phrase where I live is "the Internet is down."
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MrHenApr 28 '11 at 16:46

@MrHen I think my question applies again, there - because some might interpret it as "cutting out." My question was raised after I saw a comment "It'd be nice if the internet wasn't cutting in and out," so "cutting out."
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xdumaineApr 28 '11 at 16:53

Yes, I agree. I was merely talking about how we speak of internet outages and not your actual question (which is mostly why this is a comment and not an answer). And "cutting in and out" does sound familiar. So no argument intended. :)
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MrHenApr 28 '11 at 17:31

2 Answers
2

The general rule is "If your readers (or hearers) will understand it without the word, you can omit it. If they are going to be confused or misled without it, don't".

Out of context "internet is out" may not have that meaning: when I first read your question I read it as a fashion statement, like "The internet is no longer cool" or something. (I'm not being funny, I really did). But in context, it is fine.